• Theoretical results:
- Based on principle of growth measurement of M.aeruginosa, we have established a novel method on assessment of exterminating effect on toxic cyanobacterium – Microcystis aeruginose in an experimental condition. The methods of measuring optical density and biomass determination (chlorophyll a) are the advantageous methods for screening and selecting in order to evaluate the inhibitory effects of several plant extracts on the growth of Microcystis aeruginosa and Chlorella vulgaris algae
- From 10 plant samples selected to create a total extract applied for killing M. aeruginosa, we have identified 06 species that are able to inhibit the growth of toxic cyanobacteria. They include: Lược vàng (Callisia fragrans, M02), Củ gấu (Cyperus rotundus, M03), Củ gấu biển (Cyperus stoloniferu, M04), Cỏ lào tím (Eupatorium coelestinum, M05), Mần tưới (Eupatorium fortune, M06), and Cỏ lào (M10).
- At the testing concentrations of 500µg/ml, the extract from 06 plant samples displays a growth-inhibitory effect on M. aeruginosa and C.vulgaris. In particular, the extract from Mần tưới (Eupatorium fortune, M06) has a selecting effective action (creating the growth inhibition on M.aeruginosa but not on the growth of C. vulgaris algae).
- Using 2 fragment extracts of Mần Tưới (Eupatorium fortune, M06) for assessing the inhibition effect on the growth of phytoplankton communities and Microcysits genius in Hoan Kiem Lake at the laboratory condition showed that Ethyl acetate fragments has better effects in inhibitory than that of water fragments.
• Applied results:
- The method of assessment of exterminating effect on toxic cyanobacteria could be developed for screening other potential bioactive compounds.
- Due to its selecting effective action to the growth of toxic cyanobacterium M.aeruginosa, the extract solution from Mần tưới could be applied in the a larger scale. 
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